1. Field of the Invention
The present invention relates to a semiconductor device.
Priority is claimed on Japanese Patent Application No. 2010-103858, filed Apr. 28, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
Generally, regarding semiconductor devices, such as a DRAM, operating power-supply voltages of circuit elements have been lowered to decrease power consumption. Specifically, a power-supply voltage, which is supplied from an external unit, is lowered to a desired value in a semiconductor device, and then is supplied to circuit elements.
Recently, with the decrease in operating power-supply voltages, it has been more and more important to stabilize and supply a power-supply voltage since a variation in power-supply voltage greatly affects circuit operation. For this reason, a technique of providing a compensation capacitor between a wire for supplying a power-supply voltage and a wire for supplying a ground voltage has been used (see, for example, Japanese Patent Laid-Open Publication No. 2006-253393 and No. 2010-067661).
Regarding capacitors to be used in DRAM memory cells, on the other hand, a crown capacitor has been used in order to increase capacitance without increasing the occupied area. In the crown capacitor, inner and outer surfaces of a lower electrode are used as electrodes. Additionally, a technique of providing a supporter has been used in order to prevent collapse of lower electrodes during manufacturing processes (see, for example, Japanese Patent Laid-Open Publication No. 2008-283026 and No. 2003-297952).
The crown capacitor has an electrode structure in which inner and outer surfaces of a cup-shaped electrode are used as capacitor electrodes. A concave capacitor, as will be explained later, has an electrode structure in which only an inner surface of the cup-shaped electrode is used as a capacitor electrode.
Regarding semiconductor devices, such as a DRAM, it has been known that a capacitor, which has the same structure as of a memory cell capacitor, is used as a compensation capacitor (see Japanese Patent Laid-Open Publication No. 2010-067661). The use of a capacitor having the same structure as of a memory cell capacitor enables a reduction in the area of the compensation capacitor compared to a planar capacitor.
With the further miniaturization of recent semiconductor devices, crown capacitors with large capacitance have been used in memory cells. Accordingly, crown capacitors have been also used as compensation capacitors.
If crown capacitors are used as compensation capacitors, however, the following problems arise. Regarding miniaturized crown capacitors, collapse of lower electrodes can be prevented by a support film structure as shown in, for example, Japanese Patent Laid-Open Publication No. 2008-283026 and No. 2003-297952. However, unexpected local deformation of electrodes cannot be prevented completely.
For this reason, stress causes cracks to randomly occur in a capacitor insulating film, an upper electrode, a connection portion of a lower electrode with a support film, the support film itself, and the like in some cases. If cracks occur in an electrode and a capacitor insulating film, the amount of leak current increases, thereby causing malfunction of the predetermined circuit operation.
Regarding memory cell capacitors, a defective memory cell is detected in an operation test after manufacturing processes. Then, the defective memory cell is replaced with a new one, thereby enabling normal circuit operation. A fuse element can be used to replace the defective memory cell.
Regarding compensation capacitors, it is difficult to replace a defective portion with such a fuse element. For this reason, when a crown capacitor used in the memory cell is used as the compensation capacitor, the amount of leak current due to the capacitor structure is likely to increase, thereby causing malfunction of the predetermined circuit operation.
Accordingly, when a crown capacitor is used as a memory cell capacitor, a crown capacitor cannot be used as a compensation capacitor. Therefore, a planar capacitor, which uses a gate electrode and the like of a MOS transistor, has to be used, thereby preventing a reduction in the occupied area of the compensation capacitor.